(a) Field of the Invention
The invention relates to a respiratory tube without fastening assemblies, and more particularly, to a respiratory tube without fastening assemblies namely fastening rings, hooks, buttons, clamps, sheaths and strips. Using various structural designs of the respiratory tube, the respiratory tube without fastening assemblies is steadily stayed close to a front side of a user's head when being worn.
(b) Description of the Prior Art
Respiratory tubes for water activities such as swimming and diving come in various shapes and sizes, and are generally divided into two categories:    1. Side-worn respiratory tubes located at one side of swimmers when being worn: these respiratory tubes are the majority and most commonly seen.    2. Front-worn respiratory tubes located at a front side of swimmers when being worn: these respiratory tubes are the minority and are hardly seen.
Regarding the former respiratory tube, when the respiratory tube is worn at a side of the swimmer, apart from a water drag sectional area already present from an original volume (a body of the swimmer), an extra water drag sectional area adds up to an even larger value due to a substantial length of the respiratory tube exceeding the user's shoulder level. Consequently, water drag force is enlarged with greater strength consumed. In addition, drag force is unbalanced for that the respiratory tube is located only at one side, and movements of a swimmer at the particular side may become restricted. In the long-run, a swimmer is likely resulted with slanted strokes and thus limited advancement.
As for the latter respiratory tube, when the respiratory tube is worn at a front side of a swimmer, apart from a water drag sectional area already present from an original volume (a body of the swimmer), only a small water drag sectional area is added by a small sectional area of the respiratory tube exceeding the user's head level. Therefore, water drag force is increased with a least amount while also consuming minimum strength. In addition, because the respiratory tube is worn at a front side of the user, drag force at two sides are balance without causing issues such as restricting movements of the swimmer.
However, to maintain the respiratory tubes at appropriate positions of a swimmer's head, both of the aforesaid prior inventions require externally provided assemblies namely fastening rings, hooks, buttons, clamps, sheaths or strips, which are not parts of the respiratory tubes. These assemblies have also brought some common drawbacks:    1) water drag is increased to diminish more strength; and    2) when a swimmer's actions relative to water get faster (for example, diving at start-up or turning around), water drag is further expanded to cause disengagement or displacement of the respiratory tube, and it is necessary that the user immediately adjust the respiratory tube for continual use.
Both the aforesaid drawbacks are unfavorable for developing skills and technique refinement of swimmers.